PEOPLE infected with the deadly new coronavirus could take five days to show any symptoms, experts have said.
New research has found that the average incubation period of Covid-19 is 5.1 days.
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The experts found that almost all (97.5 per cent) of those who develop symptoms appeared to do so within 11.5 days of infection.
Coronaviruses in humans that cause common colds have average incubation periods of around three days.
Experts, led by researchers from the Johns Hopkins Bloomberg School of Public Health in the US, studied 181 cases of people confirmed to be infected with the new coronavirus, which causes the respiratory illness Covid-19.
The researchers conducted an analysis of news reports, public health reports, and press releases which included information on likely dates of exposure and when symptoms started.
Most of the cases were linked to Wuhan, the city in China at the centre of the outbreak, and the surrounding Hubei province.
The authors conclude that current “self-isolation” time frames adopted by health bodies – including the NHS – are “reasonable”.
Some people who have, or may have, been infected have been asked by health officials to stay away from others for two weeks – or “self-isolate” – to reduce the risk of the infection spreading.
The authors of the analysis said the time frame is “reasonable” but suggest that a small number of cases could develop symptoms after this quarantine period is over.
The estimates, published in the journal Annals of Internal Medicine, estimates that 101 out of every 10,000 cases will develop symptoms after 14 days of active monitoring or quarantine.
Justin Lessler, an associate professor in the Bloomberg School’s Department of Epidemiology, said: “Based on our analysis of publicly available data, the current recommendation of 14 days for active monitoring or quarantine is reasonable, although with that period some cases would be missed over the long-term.”
However, experts have warned that the study does have its limitations, such as assuming that someone becomes infected from the moment they come into contact with the virus.
Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said: “We have to acknowledge that the models they use to estimate incubation period make key assumptions, and perhaps the assumption most likely to impact on their data is that a person became infected as soon as they came into contact with the virus.
“This might not be true – the real infection timepoint might be much later, yet assuming the infection occurred at an earlier date will make the incubation period appear longer.”
Dr Ball added: “As it stands there is little evidence to suggest that a quarantine or self-isolation period of 14 days is not suitable.
“Also, there is little if any evidence that people can routinely transmit virus during the asymptomatic period.”
The 3 warning signs
As Covid-19 is a new virus, experts are still working to understand it.
According to the NHS and the World Health Organisation (WHO), early symptoms of coronavirus infection usually include:
- A cough and/or sore throat
- A high temperature
- Shortness of breath
These symptoms do not necessarily mean you have the illness and are similar to other illnesses, such as the common cold or flu.
Some people will not develop all of these symptoms – and some might not even show symptoms at all, experts have discovered.
They warn that in some people, particularly those with underlying conditions, it can cause them to develop severe complications.
These include pneumonia and swelling in the lungs, which can make it hard for the lungs to pass oxygen into the bloodstream – leading to organ failure and death.
Severe pneumonia can kill people by causing them to “drown” in the fluid flooding their lungs.